1. Field of the Invention
The present invention relates to medical systems and in particular to patient monitoring systems for collecting, storing and displaying medical data pertaining to the patient.
2. Description of the Related Art
In hospitals and other health care environments, it is often necessary to continually collect and analyze a variety of medical data pertaining to a patient. These data may include electrocardiogram signals, body temperature, blood pressure, respiration, pulse and other monitored vital signs.
Monitoring systems in the related art have typically fallen into one of two general categories: multi-function monitoring, recording and displaying systems which process and collect all of the data desired, but are bulky and difficult to transport; and small, portable systems which are easy to transport, but process and collect fewer types of data and have limited storage capability. Initially (e.g., in an ambulance or an emergency room) a patient is connected to a simple, portable monitor to observe a limited number of medical attributes, such as EKG or non-invasive blood pressure. As the patient moves to higher care facilities (e.g., an intensive care unit or operating room) it is desirable to augment these simple monitors to observe additional parameters. Generally, this is accomplished by disconnecting the patient from the simple monitor and connecting the patient to a monitoring system having more robust capabilities.
The need for continuity of data collection and display is most pressing in emergency situations. Hospital personnel want to monitor additional parameters, change the selection of parameters viewed, or retrieve trend data from the patient's history. At the same time, the patient may have to move to a different care unit. During an emergency, the speed at which a patient is transferred from a bed to an operating room or intensive care unit may substantially impact the patient's chance of survival. Accordingly, hospital personnel need to be able to quickly add functionality to the patient monitoring system and/or to quickly transfer the patient to a high performance care unit.
Two major considerations in the design of monitoring systems have been ease and speed of system reconfiguration. It is particularly undesirable to connect sensors to a patient or to disconnect them immediately prior to transportation or administration of critical procedures. U.S. Pat. Nos. 4,715,385 and 4,895,385 to Cudahy et al. discuss a monitoring system which includes a fixed location display unit and a portable display unit. A digital acquisition and processing module (DAPM) receives data from sensors attached to the patient and provides the data to either or both of the fixed and portable display units. The DAPM remains attached to the patient during patient transport, eliminating the need to remove intrusive devices from the patient before transport and to reconnect the devices after transport. Normally, the DAPM is inserted into a bedside display unit located near the patient's bed. An electrical connection to the bedside display is formed when the DAPM is inserted into the bedside display. In order to place the DAPM in the bedside monitor, sufficient cable length is provided between the sensors and the DAPM to reach the bedside display unit.
To enable insertion of the DAPM into the bedside monitor, the lines transmitting the analog data signals from the patient to the DAPM are long enough to reach from the patient to the bedside monitor. This cable length may allow the analog signals to be corrupted with noise due to, for example, radio frequency interference (RFI) from external sources.
Furthermore, the digital acquisition and processing module of the Cudahy et al. system has a fixed parameter configuration, and if the parameter requirements change due to a change in condition of the patient, the digital acquisition and processing module must be disconnected and a different module including the new parameters which are required to be monitored must be connected. This process is not only time consuming, due to the reconnection of the sensors and cables between the patient and the module, but also destructive of data, since patient data acquired in the first processing module is lost when that module is disconnected. Furthermore, the processing module of Cudahy et al. is bulky and, so, difficult to position near a patient. In addition, the Cudahy et al. processing module requires extensive cabling to the different patient sensors, which further adds to the complexity and set-up time of the system and makes it more difficult to care for the patient.
Besides the time delays which may be encountered when adding sensors to the monitor configuration, systems in the prior art also leave much to be desired with respect to cable management. As the number of sensors attached to the patient grows, so does the number of wires between the patient and the monitoring means. This network of wires makes it difficult to navigate the space around the patient's bed. Data acquisition modules or cartridges for collection of blood pressure data from invasive sensors (e.g., those using a catheter) have an additional disadvantage. Each pressure transducer is coupled to the patient by a hose which conveys fluid, and the transducer is coupled to monitoring means by an electrical wire. The transducers are desirably positioned at the height of the patient's heart to properly measure pressure in the right or left atrium. If the patient's position changes, transducer height must follow the patient's heart to maintain the accuracy of the measurements.
One solution to the problem of positioning the transducer is disclosed in European patent application No. 91201792.8 by van den Berg. This application describes a junction box adapted to receive four pressure transducers, on the outside surface. The wires from each transducer extend into the junction box. A single cable with a multiple connector plug (multiplug) extends out of the junction box and is coupled to monitor means. A clamp provides means for adjusting the height of the transducers.
Another problem with pressure data acquisition apparatus has been the location of the controls for calibrating the blood pressure transducers. In most currently available systems, these controls are located on the monitoring means, remote from the transducers. To calibrate the transducers in a prior art system, the operator must expose the transducers to atmospheric pressure. Then the operator must walk around the wires to the monitor in order to reset the pressure value displayed on the monitor to zero. Then the operator must walk back around the wires to the transducers and close them off against the atmosphere. This is a time consuming procedure. To solve this problem, some systems have included foot pedal controls coupled to the monitor, to enable the operator to send a pressure zero signal to the monitor while working at the patient's bedside.
A similar problem has been experienced when measuring pulmonary artery wedge pressure. To measure wedge pressure, a catheter having a small inflatable balloon at its tip is passed into the pulmonary artery. The balloon is inflated and the catheter is swept by blood flow further into the pulmonary artery where it wedges, obstructing blood flow. The pressure between the balloon and the left atrium (across the pulmonary capillaries and pulmonary vein) falls off to match the left atrial pressure. Typically, the controls to initiate wedge pressure measurement have been located at the monitor. To initiate the measurement, the operator must position the balloon catheter in the patient and inflate the balloon. Then the operator must then walk around the wires to the monitor and actuate the wedge start switch.
Another aspect of prior art data acquisition devices is that they are not standalone devices. An example is the Sirecust.TM. cartridge system manufactured by Siemens Medical Equipment. In this system, patient medical data are collected by one or more multiparameter cartridges. In order to display the data, the cartridges are inserted into a SIREM.TM. module box. The large size of the module box makes it impractical to place the box on or above the bed; it typically must be placed beside the bed, and may get in the way of hospital personnel who are treating the patient. Not only is the box in the way, but as noted above, an array of cables between the cartridge and the patient further interferes with movement of hospital personnel. The Hewlett-Packard Merlin.TM. system and the Marquette TRAM.TM. systems are similar in that they also require insertion of a cartridge into a module box to display data on a bedside monitor. The Cudahy patent has a similar limitation: the DAPM must be inserted into the fixed (bedside) display to display data collected by the DAPM. None of these is a standalone device.
Additional simplification is desired, in order to reduce the network of wiring and hoses surrounding the patient. Simplification of the controls for operating pressure data acquisition transducers is also desirable.